Agree. Discus, like angelfish, are shoaling fish, meaning they naturally live in groups. They have a definite social structure within a group, sometimes including a pecking order. This is natural to the fish, and denying the fish what they are programmed by natural evolution to expect can often cause stress and poor health. A group of 5 or more in a minimum 4-foot tank, with suitable tankmates of course, is the best situation. Unless as Mina says, it is a breeding pair.

30 gal. and would like to some angels in it too. but i would like to put 2 discus fish in it but can buy only one at a time

You will eventually have problems with either of those fish in a 30 gallon. Both have essentially the same requirements except discus being much more sensitive. You need a much larger tank for a group. If you have just two they must be a breeding pair. This in itself poses an issue as breeding pairs tend to breed and when they do they get highly territorial of ANY other fish near their eggs. Mixing either of those fish in that size tank is going to eventually end badly. My bets would be on the angels in the end.

I took out all the water in my 30 gallon tank about a week ago, because was merky, and it would not cycle, put fresh water in it, now is it possible that the tank has cycled already? the ph is high, the ammonia is 0.50, the nitrites are 0, and the nitrates are 0

I took out all the water in my 30 gallon tank about a week ago, because was merky, and it would not cycle, put fresh water in it, now is it possible that the tank has cycled already? the ph is high, the ammonia is 0.50, the nitrites are 0, and the nitrates are 0

If the tank was already cycled, removing the water and replacing it will not affect the nitrifying bacteria. How long has this tank beeen running? And with fish, or some other means of cycling? The ammonia is a concern, if fish are present; in a high pH that is very toxic.